Rotary press-molding apparatus

ABSTRACT

A combination, provided in a conventional punch-and-die type rotary tableting machine, of auxiliary rollers attached to each of the punches or the sheathes thereof, and tracking rails capable of exerting pressure on said punches through said auxiliary rollers with sequential transferring of the punches, serves to cause auxiliary (preparatory and complementary) compacting of material to be molded or of already molded articles resulting in a tableting performance free of capping or lamination.

United States Patent Maekawa et al.

[ 51 May 16,1972

ROTARY PRESS-MOLDING APPARATUS Inventors: Hldeyukl Maeltnwa, Osaka; Teruo Salulmoto; Yoshihlsa Sagnwa, both of Hirakata, all of Japan Assignee: Shionogi 8: Co., Ltd., Dosho-Machi Higashi-ku Osaka Pref., Japan Filed: June 2, 1970 Appl. No.: 42,687

Foreign Application Priority Date June 12, 1969 Japan ..44/46583 {1.8. Ci "425/345, 425/128 ..B29c 3/02 Field of Search ..18/20 T, 20 RR, 20 P, 4 B,

18/5 A, 5 RR [56] References Cited UNITED STATES PATENTS 2,944,493 7/ 1960 Bailey et al 18/20 T X 2,973,555 3/1961 Schwepke 18/20 'I FOREIGN PATENTS 0R APPLICATIONS 551,811 11/1956 Italy ..18/20 RR Primary Examiner-Robert L. Spicer, Jr. Attorney-Wenderoth, Lind & Ponack 57 ABSTRACT A combination, provided in a conventional punch-and-die type rotary tableting machine, of auxiliary rollers attached to each of the punches or the sheathes thereof, and tracking rails capable of exerting pressure on said punches through said auxiliary rollers with sequential transferring of the punches, serves to cause auxiliary (preparatory and complementary) compacting of material to be molded or of already molded articles resulting in a tableting performance free of capping or lamination.

1 Claim, 7 Drawing Figures INVENTOR 5 PATENTEDMAY 16 m2 sum 1 OF 3 Um F U H E Q U H n .H HUM c 6. gm 8 H w QM A M M m 3 L P 3 3 25E: 2% 55m E :55: 29: E

mun 150cm HIDEYUKI MAEKAWA, TERUO SAKAMOTO and YOSHIHISA SAGAWA,

alwdkaflz M ATTORNEY s U? c u 7 HT it hm Hun W a Un A a UT g a Q 1 mmwzmmni ROTARY PRESS-MOLDING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to production of molded articles such as medicinal tablets and has for its object the provision of an improved apparatus for the production of such articles. Particularly, the invention concerns a novel apparatus capable of effecting improved tableting performance on such materials as have hitherto proved difficult to mold and uses fewer compressing operations with a higher speed of formation of the tablets.

Throughout this specification and the appended claims, we shall use to the term "tablet" to include any compressed moldings of foods, pharmaceuticals, agricultural chemicals, powdered metals, ceramics, plastics and the like, including those which are mechanically compressed to form sufficiently firm bonding: prior to sintering thereof or coating thereover, and the term tableting" to include any process for producing the aforedefined moldings.

2. Description of the Prior Art In manufacturing molded articles such as a tablet using a conventionally known punch-and-die type rotary compressing machine, it has been customarily preferable to make the compressing velocity of the punches as low as possible as well as to prolong the dwelling period of the punches at their compacting extreme insofar as is compatible with economic production.

However, operational conditions involving the aforesaid customary operational mode, Le, a low compressing velocity and a long compression period inevitably conflict with each other and further conflict with the requisites of a high speed molding operation, and an advance in the art capable of permitting the production of tablets of high quality, using high compressing velocity and a short compression dwelling period, has long been awaited.

SUMMARY OF THE INVENTION It is therefore the primary object of the present invention to provide a rotary press molding apparatus capable of a highspeed compression molding operation while suppressing lamination and capping of the finished tablet. (capping" means a cap-like crack while lamination" means stratiformal collapse of tablets) It is another object of the present invention to provide an apparatus which can accomplish the aforedefined object without substantial difficulty.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of the present invention and attendant advantages thereof will be made apparent, to those who are conversant with the art to which the present invention pertains, by the following disclosure of the specification and the appended claims, taken in conjunction with the accompanying drawings, in which:

FIGS. 1 through 5 are graphic diagrams elucidating the experimental results on which the present invention is based,

FIG. 6 is a vertical rectilinear fragmentary sectional view of the structure composed of essential components of the invention, including a rotational structure, which is extended and projected as an embodiment of the present invention, and

FIG. 7 is a partially sectional elevation of the embodiment shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to find a clue for solving the aforedefrned problems, the present inventors have carried out a detailed investigation concerning the influence of the manner of compression defined in terms of the magnitude of the exerted pressure and the lapse of time during the exertion, on the hardness of the finished tablets and the "recovery from distortion using corn starch as a sample material, the results of which are summarized in the graphic diagrams of FIGS. 1

through 5, wherein the hardness" can be expressed as breaking strength represented by the load in kilograms exerted to break the tablet, it being regarded that the larger the value thereof the stronger the durability of the tablet against breaking, while the recovery from distortion" can be expressed as the magnitude of the expansion of the tablet after it has once been compressed to 4 mm thickness, it being regarded that the smaller the value thereof the less the occurence of capping or lamination.

The values of the hardness represented by columns A, through F respectively in FIG. 1 and those of the recovery from distortion represented by columns A, through F, respec tively in FIG. 2 correspond to each of the patterns of the compression represented by A, through F in FIG. 3.

The patterns of the compression shown in FIG. 3 are schematic graphs wherein the ordinates (non-linear graduation) represent the magnitude of pressure exerted during the compressing operation and the abscissa represent time. Each acute peak appearing in the figures corresponds to a major compression by means of the main compression rollers (Ca. 2,000 Kg per one tablet having a diameter of 5-15 mm) and each of the plateaux appearing in graphs B, D, E and F corresponds to the auxiliary compression (Ca. 300 Kg).

As can be clearly seen from the schematic graphs, the auxiliary compression exhibits advantageous results on the compressing operation and the characteristics of the finished products.

FIGS. 4 and 5, illustrate the influence of the auxiliary compression (P,) on the hardness and the recovery from distortion, respectively, in terms of the varying pressure, assuming that the compression pattern is like that of B of FIG. 3. As shown, the auxiliary compression is effective over a very wide pressure range from 300 to 1,200 Kg, per tablet and the possibility of exhibiting a great effect is expected even with a very low pressure compared to that of the major compression by the compressing rollers.

The present invention is based on the results of the previously described investigation while utilizing the construction of the known conventional rotary tableting machine of the punch-and-die type.

According to the present invention, there is provided a punch-and-die type rotary press-molding apparatus generally including in combination: a stationary frame, a laminated rotational structure composed of upper and lower punch blocks and an interposed die block each having a multiplicity of upper punches, lower punches and die cavities, respectively, around the circumference thereof, rotatably mounted around a vertical axis on said stationary frame, at least one pair of spaced opposed upper and lower compressing rollers, one above and one below the rotational structure, mounted rotatably around axes which intersect said vertical axis on said stationary frame holding said rotational structure and capable of exerting pressures on said punches. The apparatus includes an improvement which comprises; an auxiliary roller on each of the punches or the sheathes thereof and tracking rails on the stationary frame of the apparatus which rails are capable of exerting a pressure on said punches through said auxiliary rollers upon rotation of the rotational structure i.e., upon the sequential transferring of the punches around the axis of the rotational structure.

In the following paragraphs, the present invention will be described in more detail by way of example illustrated in FIGS. 6 and 7 of the drawings.

FIG. 6 is a vertical rectilinear fragmentary sectional view of the structure composed of essential members of the machine including the rotational structure (punch and die blocks) extended and projected onto a plane which is tangential to the cylindrical surface containing the circular track along which said punches and die cavities are transferred, compressing rollers, guide rails and overriders, delineated with the assumption that the right extreme of the drawing is connected to the left extreme thereof and that the punches, die cavities, and the members carrying these components are continuously transferred from the left to the right by rotation of the rotational structure. More precisely, successive conditions in the tableting cycle of a pair of punches, relative to the die cavity in which they are operative, are shown by the successive representations from left to right on the diagram, designated by successive position numerals (the last two figures of three figures numbers e.g., 02 of 202,302 or 402).

According to the present invention, a number of the conventional parts and construction which are customary to any known rotary compressing machines can equally be employed in a practical apparatus without any major modification.

To give more detail; an assembly of rotational structures (including turntable or punch blocks and die blocks) 5153, is pivoted around the vertical axis of the stationary frame 1 of the apparatus, which assembly holds multiplicities of the upper and lower punches or the sheathes therefor. in this embodiment, the punches are shown as being integrally formed with the sheathes but these are generally separable. The punches and sheathes are hereinafter called punch numbers. The upper punch members are represented by numerals 201 through 217 and the lower punch members by numerals 301 through 317, and the die cavities by 401 through 417. The interior of each die cavity is able to conform to the heads of said upper and lower punch members. Rotational movement caused by an unshown driving mechanism causes a circular movement of each pair of said punch members and dies around the circumference in a horizontal plane.

Although the rotational structure is shown in FIG. 6, as having a laminated construction composed essentially of three stories, namely the upper story or upper punch block 51, holding the upper punch members 201 through 217 while permitting their vertical movement, the middle story or die block 52 fixedly holding the die cavities 401 through 417 and the lower story or lower punch block 53 holding the lower punch members 301 through 317 equally permitting their vertical sliding movement, the structure is practically an integral member, or at least functions as one member, because its purpose is to enable the transferring of each combination of punch members and die in parallel while keeping them in a single vertical line.

Along the track of the circular movement of the punch members in the horizontal plane, there is provided two pairs of compression rollers 61 62 and 63 64, each pair being spaced opposed with a roller on either side of the rotational structure, and capable of exerting compressing pressure upon the punch members. In other words, the illustrated apparatus has two major sequentially operable compressing stages.

Besides the above described circular movement, the punch members 201 through 217 and 301 through 317 are required to have the capability of vertical movement to perform operations preparatory or complementary to the major compression, in other words, movements for charging materials to be molded into the die cavities and for ejecting the finished tablets as well as the other attendant movements.

In order to enable such incidental operation, tracking rail 7 and overriders 81 and 82, cooperating with said punch members, are installed on the stationary frame 1 of the apparatus in accordance with their required function.

Moreover, a feeder 9 for charging material 8 to be molded into the die cavity and a deflecting baffle 11 capable of deflecting the tablet molded and thrust up over the surface of the die block 52, are provided and pertinent positional relationships are maintained between them.

Although it may be a minor detail, and is therefore indicated by dotted lines, extentions 82' and B2" of the overrider 82, which can be installed in conventional machines in order to prevent the lower punch members from falling, will be made dispensable by the adoption of the present invention.

With the above described conventional construction, ordinary tableting operations can adequately be carried out. Namely, the die cavity supplied with the material 8 to be molded by the feeder 9 at the position 401 at the left extreme of P10. 7, combines with the upper and lower punch members to compress the material at the positions 203 through 205, 303 through 305 and 403 through 405 while being transferred to the right in the drawing to the positions 207, 307 and 407 where the material is subjected to a compression by the rollers 61 and 62. The combination of the punch members and die further travels to the right while holding the material once compressed therein and is subjected again to a compression by the rollers 63 and 64 at their positions 211, 311 and 411 and further continues to travel while the lower punch members is thrust up together with the molded tablet 10 and the upper punch members by the overriders 81 and 82 which contact the root portions of the lower punch members at the positions 312 through 315.

The upper punch member also begins to be thrust up by the tracking rail 7 at the positions from 214 et. seq. and finally comes to a position where it leaves an adequate clearance above the molded article 10 which is pushed up over the surface of the middle story or die block 52 of the rotational structure at the positions 215 et.seq.

In this condition, the molded article 10 is swept away from the track by the deflecting baftle 11 and is transferred to an unshown receptacle or subsequent processes.

According to the special feature of the present invention, upper and lower punch members, each provided with a roller whose diameter is neariy equal to that of the punch member therefor as is indicated by numerals 2010 through 2174 and 3010 through 3170, are employed in addition to the above described conventional members and construction. Simultaneously, a plurality of semi-annular tracking rails 121, 122, 123 and 124, cooperative with said auxiliary rollers, are installed on the stationary frame 1 of the apparatus. The tracking rail 121 contacts the upper punch members in the positions 204 through 210 at their rollers 2040 through 2100 while the tracking rail 123 contacts the lower punch members in the positions 304 through 31 1 at their rollers 3040 through 311a. Furthermore, the tracking rail 122 contacts the upper punch members in the positions 212 through 214 at their rollers 212a through 214a while the tracking rail 124 contacts the lower punch members in the positions 312 through 314 at their rollers 312a through 3140.

Each of the junctions between the auxiliary rollers and punch members is made so that it can withstand a pressure load of at least 300 Kg. As is shown in FIG. 7, each of the tracking rails is installed on abutments 121a through 1240 projecting from the stationary frame of the apparatus through suitable resilient means such as springs 121s through 124s so that they can always keep good contact with the rollers.

In addition to an ordinary tableting operation as is performed by the conventional apparatus, the apparatus of the illustrated embodiment operates as follows; the combination of the die cavity and upper and lower punch members receives, while holding the material to be molded therein, auxiliary compressions due to the contact between the tracking rails and the auxiliary rollers at the positions before the first major compression, between both the major compression and after the second major compression, and these operation can be regarded as preparatory fastening, and complementaly or confirmatory compactings.

As previously described, material to be molded receives a compression which corresponds to the compression pattern F of FIG. 3 during the travel.

The excellence of the molded articles processed in accordance with such compression pattern is already illustrated in the foregoing paragraphs of the specification.

Of these auxiliary compressions, a particular importance is placed the one after the second major compression where the upper and lower punch members at the positions 212 through 214 and 31 2 through 314 are thrust upwards all together while being kept in almost parallel relationships.

Although an apparatus having two stages of major compression wherein its rotational structure includes a single tableting line is shown in the above disclosure, the present invention is also applicable to ones having a single compression stage or ones having three or more compression stages, or machines having two or more tableting lines, operative in sequence in a single rotational structure which is conventionally called a double type machine." Moreover, the shape or construction of the major compression rollers is not limited to the simple cylindrical column as shown in the drawings, but rollers of any other shape such as a frusto-conical shape capable of prolonging the dwelling period of the punches at their compacting extreme, can also be employed without major modification.

We claim:

1. A punch-and-die type rotary compression molding apparatus which comprises; a stationary frame, a structure rotatably mounted around a vertical axis on said stationary frame and composed of upper and lower punch blocks and an interposed die block, each having a multiplicity of upper punch members, lower punch members and die cavities, respectively, around the circumference thereof, at least one pair of upper and lower compressing rollers, disposed one above and one below the rotatable structure, and mounted rotatably around axes which intersect said vertical axis, and capable of exerting pressures on said punch members, an auxiliary roller on each of the punch members, a plurality of divided semi-annular tracking rails installed, a plurality of abutments projecting outwardly from the stationary frame, and resilient means on said abutments and on which said tracking rails are mounted, said auxiliary rollers engaging said tracking rails for exerting a pressure on said punch members through said auxiliary rollers upon sequential movement of the punch members around the axis of the rotatable structure.

l l 1 I! I 

1. A punch-and-die type rotary compression molding apparatus which comprises; a stationary frame, a structure rotatably mounted around a vertical axis on said stationary frame and composed of upper and lower punch blocks and an interposed die block, each having a multiplicity of upper punch members, lower punch members and die cavities, respectively, around the circumference thereof, at least one pair of upper and lower compressing rollers, disposed one above and one below the rotatable structure, and mounted rotatably around axes which intersect said vertical axis, and capable of exerting pressures on said punch members, an auxiliary roller on each of the punch members, a plurality of divided semi-annular tracking rails installed, a plurality of abutments projecting outwardly from the stationary frame, and resilient means on said abutments and on which said tracking rails are mounted, said auxiliary rollers engaging said tracking rails for exerting a pressure on said punch members through said auxiliary rollers upon sequential movement of the punch members around the axis of the rotatable structure. 